Tuesday, March 28, 2006

ClockNews - Adolescent Sleep

"The parents get stigmatized as not having control over their kids when they can't get them to school in time," says James Wyatt, co-director of the sleep-disorders center at Rush University Medical Center in Chicago who is conducting research looking for ways to better diagnose the disorder. "Children themselves get stigmatized as avoiding school or lazy. There's a lot of baggage associated with it."

An optimal night's sleep for teens is nine hours, said Mary Carskadon, director of the E.P. Bradley Hospital Sleep center at Brown University and the other study author. But researchers found that almost half slept fewer than eight hours on school nights.

As kids reach adolescence, their internal clocks tend to shift, causing them to naturally feel more alert later at night and to wake up later in the morning. This change can make it difficult for them to fall asleep before 11 p.m. In fact, more than half of high school students stay up past that hour on school nights.

Sleep experts continue to advocate for later school starting times, 9 a.m. or after, a notion that hasn't been embraced by Valley districts.

"Sending students to schools without enough sleep is like sending them to school without breakfast," said Jodi Mindell, associate director of the Sleep Disorders Center at the Children's Hospital of Philadelphia and co-chair of the sleep poll task force. "Sleep serves not only as a restorative function for the adolescents' bodies and brains, but it is also a key time when they process what they've learned during the day."

"Our results show that the adage 'early to bed, early to rise' presents a real challenge for adolescents," says Carskadon, who directs the Bradley Hospital Sleep and Chronobiology Sleep Laboratory and is a professor of psychiatry and human behavior at Brown Medical School.

Carskadon's work has been instrumental in influencing school start times across the country. Regionally, the North Kingstown School Department in Rhode Island, North Reading Public Schools in Massachusetts, and West Hartford Public Schools in Connecticut are considering school start time changes due, in part, to research on teens and sleep.

In a study published in the November 2005 issue of the journal Sleep, Carskadon found that the "sleep pressure" rate the biological trigger that causes sleepiness slows down in adolescence and is one more explanation for why teens can't fall asleep until later at night. Carskadon's newest finding indicates that, in addition to the changes in their internal clocks, adolescents experience slower sleep pressure, which may contribute to an overall shift in teen sleep cycles to later hours.

At least one of the reasons adolescents don't get enough sleep is not their fault, said Mindell. Hormone changes cause a two-hour shift in circadian rhythm (the body's internal clock), Mindell said. So they are naturally more alert later in the day.

Nature provides at least a partial excuse. When children reach adolescence, their circadian rhythms, or internal clocks, shift, making them more awake at night. Sixth-graders got 8.4 hours on school nights, the survey found. By contrast, seniors in high school slept an average of 6.9 hours on school nights.

The report indicated that adolescents aged 13 to 22 need nine to 10 hours of sleep each night. It also discussed the hormonal changes that conspire against them. When puberty hits, the body's production of sleep-inducing melatonin is delayed, making an early bedtime biologically impossible for most teens. At the same time, the report notes, external forces such as after-school sports and jobs and early school start times put the squeeze on a full night's sleep.

The result: A "profound negative effect" on mood, school performance and cognitive function. Studies also show that young people between 16 and 29 years of age were the most likely to be involved in crashes caused by the driver falling asleep.

Most teens miss sleep because of the normal changes of adolescence, compounded by distraction. Sleep specialists speak of circadian rhythms, or the body's internal clock. As children reach their teens, that clock shifts: They are wider awake later at night, and prone to sleep later in the morning. This "phase delay" makes it difficult to fall asleep before 11 p.m.

School schedules, on the other hand, are built around busing needs and plans for daylight sports events, among other things. Most teens must get up around 6:30 or 7 a.m. to make it to school on time.

"In the competition between the natural tendency to stay up late and early school start times, a teen's sleep is what loses out," said Jodi A. Mindell of St. Joseph's University in Philadelphia.------------------------Some school districts, most notably the Minneapolis public school district, have been trying later start times for high schools, Assuras reports. Researchers have seen some benefits, but in many school districts, conflicts with bus schedules and after-school activities make such changes extremely difficult.

Assuras says, short of getting school start times changed, teens might want to take some advice from experts, who recommend saying goodbye to the entertainment zone in the bedroom, cutting out caffeine after lunchtime, setting up a daily sleep and wake-time routine, and being aware that trying to catch up by sleeping in on weekends throws off your natural body rhythm.

As children reach adolescence, their circadian rhythms -– or internal clocks -– tend to shift, causing teens to naturally feel more alert later at night and wake up later in the morning. A trick of nature, this "phase delay" can make it difficult for them to fall asleep before 11 p.m.; more than one-half (54 percent) of high school seniors go to bed at 11 p.m. or later on school nights. However, the survey finds that on a typical school day, adolescents wake up around 6:30 a.m. in order to go to school, leaving many without the sleep they need.

"In the competition between the natural tendency to stay up late and early school start times, a teen's sleep is what loses out," notes Jodi A. Mindell, PhD, co-chair of the poll task force and an NSF vice chair. "Sending students to school without enough sleep is like sending them to school without breakfast. Sleep serves not only a restorative function for adolescents' bodies and brains, but it is also a key time when they process what they've learned during the day." Dr. Mindell is the director of the Graduate Program in Psychology at Saint Joseph's University and associate director of the Sleep Center at The Children's Hospital of Philadelphia.

The researchers said that as children reach puberty, their body clocks tended to readjust to start two hours later, so they are more alert at night and sleepier in the early morning. Mindell and Carskadon said schools should adjust their schedules accordingly, and start later. A few have done so, they said, and found that instead of staying up later, students sleep longer.

"Some of our kids are literally sleep-walking through life, with some potentially serious consequences," Millman said. "As clinicians and researchers, we know more now than ever about the biological and behavioral issues that prevent kids from getting enough sleep.